Inorganic filler containing polyolefin composition

ABSTRACT

An inorganic filler-containing polyolefin composition which comprises 
     100 parts by weight of a polyolefin, 
     1-100 parts by weight of an inorganic filler. 
     0.01-1.0 part by weight of a phenolic antioxidant represented by the general formula (I) shown below, and 
     at least one compound selected from the group consisting of the compounds represented by the general formulas (II) to (IV) shown below, and optionally 0.01-1.0 part by weight of a sulfur antioxidant and/or 0.01-2.0 parts by weight of a light stabilizer. ##STR1##  wherein R 1  represents an alkyl group of 1-3 carbon atoms, 
     
         R.sub.2 --CO--NH--(CH.sub.2).sub.n --HN--CO--R.sub.2       (II) 
    
      wherein R 2  represents an alkyl group or an alkenyl group of 5-21 carbon atoms, and n is an integer of 1 to 6. 
     
         R.sub.3 --COHN.sub.2                                       (III) 
    
      wherein R 3  represents an alkyl group or an alkenyl group of 5-21 carbon atoms. ##STR2##  wherein R 4  represents an alkyl group, an alkenyl group or an acyl group (R&#39;-CO) of 8-18 carbon atoms, m and n are integers which meet m+n=2 to 10, R&#39; represents an aliphatic carbon chain which may be saturated or unsaturated, and R 5  represents an alkyl group or an alkenyl group of 7-17 carbon atoms. 
     Excellent thermal-oxidation stability and/or light stability are obtained.

The present invention relates to a polyolefin composition containing inorganic fillers, which is excellent in thermal-oxidation stability and light stability.

Inorganic fillers are widely used in order to improve polyolefins in mechanical properties such as stiffness, impact resistance, dimension stability and heat resistance.

However, inorganic fillers considerably deteriorate thermal-oxidation stability and light stability of polyolefins. Thus, there is a need to improve such defect.

In order to improve the deterioration of thermal-oxidation stability and light stability, various methods have been proposed as disclosed in Japanese Patent Publication (Kokai) Nos. 52-49254, 52-80345, 53-79938, 56-90844, 56-118437, 56-141339 and 62-273239. However, these methods are still insufficient.

The reason why the system containing inorganic fillers is low in thermal-oxidation stability and light stability is considered to be that inorganic fillers inactivate thermal-oxidation stabilizers and light stabilizers so that they cannot effectively function.

Under such circumstances, it is an object of the present invention to provide a polyolefin composition containing inorganic fillers, which overcomes the conventional defects in thermal-oxidation stability and light stability.

The present invention provides an inorganic filler-containing polyolefin composition which comprises 100 parts by weight of a polyolefin, 1-100 parts by weight of an inorganic filler, 0.01-1.0 part by weight of a phenolic antioxidant represented by the general formula (I) shown below, and at least one compound selected from the group consisting of the compounds represented by the general formulas (II) to (IV) shown below. ##STR3## wherein R₁ represents an alkyl group of 1-3 carbon atoms,

    R.sub.2 --CO--NH--(CH.sub.2).sub.n --HN--CO--R.sub.2       (II)

wherein R₂ represents an alkyl group or an alkenyl group of 5-21 carbon atoms, and n is an integer of 1 to 6,

    R.sub.3 --CONH.sub.2                                       (III)

wherein R₃ represents an alkyl group or an alkenyl group of 5-21 carbon atoms, ##STR4## wherein R₄ represents an alkyl group, an alkenyl group or an acyl group (R'--CO) of 8-18 carbon atoms, m and n are integers which meet m+n=2 to 10, R' represents an aliphatic hydrocarbon chain which may be saturated or unsaturated, and R₅ represents an alkyl group or an alkenyl group of 7-17 carbon atoms.

This compound is excellent in thermal-oxidation stability.

The present invention also provides an inorganic filler-containing polyolefin composition which comprises 0.01-1.0 part by weight of a sulfur antioxidant in addition to the above-mentioned composition. This composition is also excellent in thermal-oxidation stability.

The present invention further provides an inorganic filler-containing polyolefin composition which comprises 0.01-2.0 parts by weight of a light stabilizer in addition to one of the above-mentioned composition. This composition is excellent in light stability as well as thermal-oxidation stability.

The polyolefin used in the present invention includes homopolymer of α-olefin such as ethylene, propylene, butene-1, hexene-1 or 4-methyl-pentene-1, and random or block copolymer comprising two or more of such α-olefins as listed above. Examples of the polyolefin are polyethylene, polypropylene, polybutene-1, polyisobutene, poly-3-methyl-butene-1, poly-4-methyl-pentene-1, ethylene-propylene copolymer, ethylene-butene-1 copolymer, propylene-4-methyl-pentene-1 copolymer, propylene-butene-1 copolymer, decene-1-4-methyl-pentene-1 copolymer, ethylene-propylene butene-1 copolymer, etc. In the case of copolymer, comonomer may be multiunsaturated compound such as conjugated or non-conjugated dienes or acrylic acid, methacrylic acid, vinyl acetate or the like. These polymers further include modified ones with acid, for example, polymers graft-modified with α,β-unsaturated aliphatic acid, cycloaliphatic carboxylic acid or derivatives thereof and also include rubbery, fatty and waxy polymers.

In the present invention, the polyolefin may be a mixture obtained by adding to an above-mentioned polyolefin a synthetic rubber, depending upon an application. The synthetic rubber which may be used in the present invention is preferably ethylene-α-olefin copolymer rubber, for example, copolymer rubbers of ethylene and α-olefin, e.g., propylene, butene-1 or hexene-1; or ternary copolymer rubber (hereinafter referred to as EPDM) in which non-conjugated dienes, for example, ethylidene norbornene or cyclopentadiene is copolymerized as the third component with the ethylene-propylene copolymer. Among them, ethylene-propylene copolymer rubber and EPDM are most preferred.

The inorganic filler which can be used in the present invention include, for example, talc, mica, wollastonite, calcium carbonate, barium sulfate, magnesium carbonate, clay, alumina, silica, calcium sulfate, carbon fibers, glass fibers, metal fibers, silica sand, carbon black, titanium oxide, magnesium hydroxide, zeolite, molybdenum, diatomaceous earth, sericite, white sand, microballoon, calcium hydroxide, calcium sulfite, sodium sulfate, bentonite and graphite. Among them, talc, mica, glass fibers, wollastonite and the like are preferred for improving impact resistance at low temperature, moldability and paintability.

The amount of inorganic fillers to be added is 1-100 parts by weight, preferably 5-80 parts by weight, based on 100 parts by weight of polyolefin. If the amount is more than 100 parts by weight, moldability deteriorates when a molded article is produced, or appearance of the molded article is degraded even though it can be molded. If the amount is less than 1 part by weight, mechanical properties such as stiffness, dimension stability and heat stability of molded articles are not sufficiently improved.

The phenolic antioxidant represented by the general formula (I): ##STR5## includes, for example, compounds shown by the following formulas: ##STR6##

These phenolic antioxidants impart thermal-oxidation stability to inorganic filler-containing polyolefins more effectively than other phenolic antioxidants.

The sulfur antioxidant used in the present invention includes dilauryl-thio-dipropionate, dimyristyl-thio-dipropionate, distearyl-thio-dipropionate and pentaerythritol tetrakis(β-laurylthiopropionate). Among them, pentaerythritol tetrakis(β-laurylthiopropionate) is preferred.

When the sulfur antioxidant is used together with the phenolic antioxidant in a ratio of the latter to the former of 1:3-4, the most significant effect is obtained.

The amount each of the phenolic antioxidant represented by the formula (I) and the sulfur antioxidant is each 0.01-1.0 part by weight, preferably 0.05-0.8 part by weight, based on 100 parts by weight of polyolefin. If it is 1.0 part by weight or more, fuming sometimes occurs during molding process or bleed out may appear on the surface of molded articles, and also it is economically inadvisable. If it is 0.01 part by weight or less, the effect of the present invention cannot be sufficiently attained.

The light stabilizer used in the present invention includes salicylate compounds, benzophenone compounds, benzotriazole compounds, nickel chelate compounds and hindered amine compounds. These compounds may be used alone or in combination thereof.

Examples of these compounds are 2,4-di-t-butylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, 4-octylphenyl-3,5-di-t-butyl-4-hydroxybenzoate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole, bis(2,2,6,6-tetramethyl-4-piperidyl)sebacate, polycondensate of succinic acid and dimethyl-1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine, poly[{6-(1,1,3,3-tetramethylbutyl)imino-1,1,3,5-triazine-2,4-diyl}{2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}], nickel-bis(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonato, [2,2'-thiobis(4-t-octylphenolate)]-n-butylaminenickel II and the like.

In the present invention, the amount of light stabilizer to be added is 0.01-2.0 parts by weight, preferably 0.05-1.5 parts by weight, based on 100 parts by weight of polyolefin. If it is 2.0 parts by weight or more, fuming sometimes occurs upon molding process or breed out may appear on the surface of molded articles, and also it is economically inadvisable. If it is 0.01 part by weight or less, the effect of the present invention cannot be achieved sufficiently.

It is needless to say that both the light stabilizer and the sulfur antioxidant may be used in the present invention.

Examples of the compounds represented by the general formula (II): R₂ --CO--NH--(CH₂)_(n) --HN--CO--R₂, which are used in the present invention, include methylenebisstearamide, ethylenebisstearamide, ethylenebisoleamide, hexamethylenebisstearamide and the like.

Examples of the compounds represented by the general formula (III): R₃ --CONH₂, which is used in the present invention, include lauramide, stearamide, oleamide, behenamide, erucamide and the like.

Examples of the compounds represented by the general formula (IV): ##STR7## which is used in the present invention, include compounds shown by the following formulas: ##STR8##

Addition amount of the compounds represented by the general formulas (II) to (IV) is respectively 0.01-1.0 part by weight, preferably 0.05-0.8 part by weight, based on 100 parts by weight of polyolefin. If it is 1.0 parts by weight or more, fuming sometimes occurs upon molding process or bleed out may appear on the surface of shaped articles, and also it is economically inadvisable. If it is 0.01 part by weight or less, the effect of the present invention cannot be achieved sufficiently.

It is preferred that a phosphorus antioxidant is added to the present composition since it further improves thermal-oxidation stability and light stability.

Examples of the phosphorus antioxidant are distearylpentaerythritol diphosphite, tris(2,4-di-t-butylphenyl)phosphite, bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-t-butylphenyl)4,4'-biphenylene diphosphonite and trinonylphenyl phosphite.

The composition of the present invention may contain other additives, for example, process oils, plasticizers, lubricating oils, neutralizing agents, antioxidants, heavy metal inactivating agents, lubricants, nucleating agents, antistatic agents, release agents, pigments and antifungal agents, so long as they do not make any harm to properties of the composition.

The composition according to the present invention is obtained by kneading in a heat-molten state by use of an ordinary kneading machine such as a uniaxial extruder, a biaxial extruder, a banbury mixer, a roll and a kneader.

Products obtained from the inorganic filler-containing polyolefin composition according to the present invention as described above have extremely excellent thermal-oxidation stability and light stability.

Hereinafter, the present invention will be more specifically set forth with reference to examples.

Test methods of thermal-oxidation stability and light stability in the examples were as follows:

TEST METHOD FOR THERMAL-OXIDATION STABILITY

The thermal-oxidation stability was evaluated in accordance with test method for thermal degradation of thermoplastics (oven method), general rule, prescribed in JIS K 7212. Namely, a time period (GO life) in which the test specimen of a pressed sheet having a thickness of 1 mm is completely degraded, or, in other words, in which its pull strength becomes zero, was determined at 150° C. using a gear oven manufactured by Toyo Seiki Seisakusho Kabushiki Kaisha.

TEST METHOD FOR LIGHT STABILITY

The accelerated light-resistance test was carried out using a Sunshine Super Long Life Weatherometer (model: WEL-SUN-DC) manufactured by Suga Tester Kabushiki Kaisha. Then, a time period in which any external abnormality such as crackings appears on the surface of the test specimen, was determined. The test conditions were as follows:

    ______________________________________                                         (1) Size of test specimen                                                                           Pressed sheet of 70                                                            mm × 25 mm × 1 mm (thick)                     (2) Black panel temperature                                                                         83° C.                                             (3) Spray/dry cycle  18 min/120 min                                            (4) Humidity in a tester                                                                            50% RH                                                        vessel                                                                     (5) Observation for the                                                                             microscopic observation                                       external abnormality                                                                            (×50)                                                   such as crackings                                                          ______________________________________                                    

EXAMPLES 1-12

One hundred parts by weight of powder of crystalline ethylene-propylene block copolymer (ethylene content: 7.2 wt %, melt index: 3.0 g/10 min) and the other components shown by the formulation of Table 1 were melt-kneaded in a banbury mixer at 180° C. for 10 minutes. Then, the resultant mixture was made into a sheet having a thickness of 5 mm by use of a roll and hardened by cooling, and then was pelletized by cutting.

The obtained pellets were shaped at 230° C. into a pressed sheet having a thickness of 1 mm. A disc test specimen having a diameter of 25 mm was punched out of the sheet, and its GO life at 150° C. was measured. The result is shown in Table 1.

COMPARATIVE EXAMPLES 1-15

Test specimens were prepared in the same manner as in Examples 1-12 except that the formulations shown in Table 2 were employed.

Their GO lives at 150° C. were measured. The result is shown in Table 2.

EXAMPLES 13-16

One hundred parts by weight of powder of crystalline ethylene-propylene block copolymer (ethylene content: 7.2 wt %, melt index: 3.0 g/10 min) and the other components shown by the formulation of Table 3 were melt-kneaded in a banbury mixer at 180° C. for 10 minutes. Then, the resultant mixture was made into a sheet having a thickness of 5 mm by use of a roll and hardened by cooling, and then was pelletized by cutting.

The obtained pellets were shaped at 230° C. into a pressed sheet having a thickness of 1 mm. A test specimen having a dimension of 70 mm ×25 mm was punched out of the sheet, and subjected to the accelerated light-resistance test. A time period in which external abnormality such as crackings occurs was measured. The result is shown in Table 3.

COMPARATIVE EXAMPLES 16-20

Test specimens were prepared in the same manner as in Examples 13-16 except that the formulations shown in Table 3 were employed.

The test specimens were subjected to the accelerated light-resistance test. And, time periods in which external abnormality such as crackings occurs were measured.

                                      TABLE 1                                      __________________________________________________________________________     (Examples 1-12)                                                                Formulation (part by weight)                                                   Inorganic                 Ole SDE 150° C. GO life                       filler     A-1                                                                               A-2                                                                               A-3                                                                               A-4                                                                               EBS                                                                               amide                                                                              amine                                                                              (Hrs)                                        __________________________________________________________________________     Example 1                                                                            Talc 25                                                                             0.05                                                                              0.2                                                                               -- -- 0.05                                                                              --  --  1010                                         Example 2                                                                            Talc 25                                                                             0.05                                                                              0.2                                                                               -- -- -- --  0.05                                                                                950                                         Example 3                                                                            Talc 25                                                                             0.05                                                                              0.05                                                                              0.15                                                                              -- 0.05                                                                              --  --  1460                                         Example 4                                                                            Talc 25                                                                             0.05                                                                              0.05                                                                              0.15                                                                              -- -- --  0.05                                                                               1310                                         Example 5                                                                            Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              0.05                                                                              --  --  2220                                         Example 6                                                                            Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- 0.05                                                                               --  2050                                         Example 7                                                                            Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- --  0.05                                                                               2180                                         Example 8                                                                            Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.3                                                                               0.05                                                                              --  --  3600                                         Example 9                                                                            Mica 25                                                                             0.05                                                                              0.2                                                                               -- -- 0.1                                                                               --  --   750                                         Example 10                                                                           Mica 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              0.1                                                                               --  --  1640                                         Example 11                                                                           Mica 25                                                                             0.05                                                                              0.2                                                                               -- -- 0.05                                                                              --  --   920                                         Example 12                                                                           Mica 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              0.05                                                                              --  --  2090                                         __________________________________________________________________________      A-1: Calcium stearate                                                          ##STR9##                                                                       A3: Dimyristylthio-dipropionate                                                A-4: Pentaerythritol tetrakis (β-laurylthiopropionate)                    EBS: Ethylenebisstearamide                                                     Ole amide: Methylenebisoleamide                                                SDE amine: N,Nbishydroxyethylstearylamine                                      Talc: Micron White 5000S manufactured by Hayashi Kasei Kabushiki Kaisha        Mica: S150 manufactured by Kabushiki Kaisha Repko                        

                                      TABLE 2                                      __________________________________________________________________________     (Comparative Examples 1-15)                                                                                                  150° C.                                Formulation (part by weight)     GO                                            Inorganic              Mono      life                                          filler                                                                              A-1                                                                               A-2                                                                               A-3                                                                               A-4                                                                               A-5                                                                               A-6                                                                               gly S.A.                                                                              EBS                                                                               (Hrs)                            __________________________________________________________________________     Comparative Example 1                                                                       Talc 25                                                                             0.05                                                                              0.2                                                                               -- -- -- -- --  -- -- 160                              Comparative Example 2                                                                       Talc 25                                                                             0.05                                                                              0.05                                                                              0.15                                                                              -- -- -- --  -- -- 180                              Comparative Example 3                                                                       Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- -- --  -- -- 280                              Comparative Example 4                                                                       Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.3                                                                               -- -- --  -- -- 460                              Comparative Example 5                                                                       Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- -- 0.1 -- -- 340                              Comparative Example 6                                                                       Talc 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- -- --  0.1                                                                               -- 280                              Comparative Example 7                                                                       Talc 25                                                                             0.05                                                                              -- 0.15                                                                              -- 0.05                                                                              -- --  -- 0.05                                                                              700                              Comparative Example 8                                                                       Talc 25                                                                             0.05                                                                              -- -- 0.15                                                                              0.05                                                                              -- --  -- 0.05                                                                              700                              Comparative Example 9                                                                       Mica 25                                                                             0.05                                                                              -- 0.15                                                                              -- -- 0.05                                                                              --  -- 0.05                                                                              600                              Comparative Example 10                                                                      Mica 65                                                                             0.05                                                                              0.2                                                                               -- -- -- -- --  -- --  90                              Comparative Example 11                                                                      Mica 65                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- -- --  -- -- 120                              Comparative Example 12                                                                      Mica 65                                                                             0.05                                                                              -- -- 0.15                                                                              0.05                                                                              -- --  -- 0.05                                                                              650                              Comparative Example 13                                                                      Mica 25                                                                             0.05                                                                              0.2                                                                               -- -- -- -- --  -- -- 150                              Comparative Example 14                                                                      Mica 25                                                                             0.05                                                                              0.05                                                                              -- 0.15                                                                              -- -- --  -- -- 170                              Comparative Example 15                                                                      Mica 25                                                                             0.05                                                                              -- -- 0.15                                                                              0.05                                                                              -- --  -- 0.05                                                                              650                              __________________________________________________________________________      A-1: Calcium stearate                                                          ##STR10##                                                                      A3: Dimyristylthio-dipropionate                                                A-4: Pentaerythritol tetrakis (β-laurylthiopropionate)                    A-5:                                                                           Tetrakis[methylene3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane         A-6: 1,3,5tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate                     Mono Gly: Glycerin monostearate                                                S.A.: Stearic acid (C.sub.17 H.sub.35 COOH)                                    EBS: Ethylenebisstearylamide                                                   Talc: Micron White 5000S manufactured by Hayashi Kasei Kabushiki Kaisha        Mica: S150 manufactured by Kabushiki Kaisha Repko                        

                                      TABLE 3                                      __________________________________________________________________________     (Examples 13-16 and Comparative Examples 16-20)                                                                            Light stability                           Formulation (part by weight)         (time when                                Inorganic                 SDE Mono   cracking)                                 filler                                                                              A-1                                                                               A-2                                                                               A-5                                                                               L-1                                                                               L-2                                                                               P-1                                                                               EBS                                                                               amine                                                                              gly S.A.                                                                              (hrs.)                             __________________________________________________________________________     Example 13                                                                            Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- 0.05                                                                              --  --  -- 1700                               Example 14                                                                            Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- -- 0.05                                                                               --  -- 1850                               Example 15                                                                            Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               0.1                                                                               0.05                                                                              --  --  -- 2150                               Example 16                                                                            Mica 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- 0.05                                                                              --  --  -- 1550                               Comparative                                                                           Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- -- --  --  --  950                               Example 16                                                                     Comparative                                                                           Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- -- --  0.05                                                                               -- 1100                               Example 17                                                                     Comparative                                                                           Talc 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- -- --  --  0.05                                                                              1000                               Example 18                                                                     Comparative                                                                           Talc 25                                                                             0.05                                                                              -- 0.1                                                                               0.1                                                                               0.1                                                                               -- 0.05                                                                              --  --  -- 1450                               Example 19                                                                     Comparative                                                                           Mica 25                                                                             0.05                                                                              0.1                                                                               -- 0.1                                                                               0.1                                                                               -- -- --  --  --  850                               Example 20                                                                     __________________________________________________________________________      A-1: Calcium stearate                                                          ##STR11##                                                                      A5: Tetrakis[methylene3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methan      L-1: Bis(2,2,6,6tetramethyl-4-piperidyl)sebacate                               L-2: 2(2'-hydroxy3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole             P-1: Distearylpentaerythritol diphosphite                                      EBS: Ethylenebisstearamide                                                     SDE amine: N,Nbishydroxyethylstearylamine                                      Mono Gly: Glycerin monostearate                                                S.A.: Stearic acid (C.sub.17 H.sub.35 COOH)                                    Talc: Micron White 5000S manufactured by Hayashi Kasei Kabushiki Kaisha         Mica: S150 manufactured by Kabushiki Kaisha Repko                       

EXAMPLES 17-19

One hundred parts by weight of powder of crystalline ethylene-propylene block copolymer (ethylene content: 7.2 wt %, melt index: 3.0 g/10 min) and the other components shown by the formulation of Table 4 were melt-kneaded in a banbury mixer at 180° C. for 10 minutes. Then, the resultant mixture was made into a sheet having a thickness of 5 mm by use of a roll and hardened by cooling, and then was pelletized by cutting.

The obtained pellets were shaped at 230° C. into a pressed sheet having a thickness of 1 mm. A disc test specimen having a diameter of 25 mm was punched out of the sheet, and its GO life at 150° C. was measured.

Another specimen having a dimension of 70 mm ×25 mm was also punched out of the above sheet and subjected to the accelerated light-resistance test. And, a time period in which external abnormality such as crackings occurs was measured.

The results are shown in Table 4.

COMPARATIVE EXAMPLES 21-23

Test specimens were prepared in the same manner as in Examples 17-19 except that the formulations shown in Table 4 were employed.

Their GO lives at 150° C. were measured. Also, the test specimens were subjected to the accelerated light-resistance test. And, time periods in which external abnormality such as crackings occurs were measured. The results are shown in Table 4.

                                      TABLE 4                                      __________________________________________________________________________     (Examples 17-19 and Comparative Examples 21-23)                                                                          Light stability                             Formulation (part by weight)  150° C.                                                                      (Time when                                  Inorganic                 SDE GO life                                                                             cracking)                                   filler                                                                              A-1                                                                               A-2                                                                               A-6                                                                               A-7                                                                               L-1                                                                               L-2                                                                               L-3                                                                               amine                                                                              (Hrs.)                                                                              (hrs.)                               __________________________________________________________________________     Example 17                                                                            Talc 30                                                                             0.05                                                                              0.1                                                                               -- 0.3                                                                               0.3                                                                               -- -- 0.3 2440 1120                                 Example 18                                                                            Talc 30                                                                             0.05                                                                              0.1                                                                               -- 0.3                                                                               -- 0.3                                                                               -- 0.3 3040 550                                  Example 19                                                                            Talc 30                                                                             0.05                                                                              0.1                                                                               -- 0.3                                                                               -- -- 0.3                                                                               0.3 2680 900                                  Comparative                                                                           Talc 30                                                                             0.05                                                                              -- 0.1                                                                               0.3                                                                               0.3                                                                               -- -- 0.3 1150 750                                  Example 21                                                                     Comparative                                                                           Talc 30                                                                             0.05                                                                              -- 0.1                                                                               0.3                                                                               -- 0.3                                                                               -- 0.3 1300 300                                  Example 22                                                                     Comparative                                                                           Talc 30                                                                             0.05                                                                              -- 0.1                                                                               0.3                                                                               -- -- 0.3                                                                               0.3 1240 650                                  Example 23                                                                     __________________________________________________________________________      A-1: Calcium stearate                                                          ##STR12##                                                                      A6: 1,3,5tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate                      A-7: Distearylthio-dipropionate                                                L-1: Bis(2,2,6,6tetramethyl-4-piperidyl)sebacate                               L-2: 2(2'-hydroxy3't-butyl-5'-methylphenyl)-5-chlorobenzotriazole              L-3: Polycondensate of succinic acid and                                       dimethyl1-(2-hydroxyethyl)-4-hydroxy-2,2,6,6-tetramethylpiperidine             SDE amine: N,Nbishydroxyethylstearylamine                                      Talc: Micron White 5000S manufactured by Hayashi Kasei Kabushiki Kaisha  

Polyolefin has a disadvantage that its thermal-oxidation stability and light stability were considerably lowered by the addition of inorganic fillers.

However, in accordance with the present invention, such defects have been markedly improved by adding a specific phenolic antioxidant, a specific type of compound, a sulfur antioxidant and a light stabilizer to inorganic-filler containing polyolefins. 

We claim:
 1. An inorganic filler-containing polyolefin composition which comprises(a) 100 parts by weight of a polyolefin, (b) 1-100 parts by weight of an inorganic filler, (c) 0.01-1.0 part by weight of a phenolic antioxidant represented by general formula (I) shown below: ##STR13## wherein R, represents an alkyl group of 1-3 carbon atoms, and (d) at least one compound represented by general Formula (II) shown below:

    R.sub.2 --CO--NH--(CH.sub.2).sub.n --HN--CO--R.sub.2       (II)

wherein R₂ represents an alkyl group or an alkenyl group of 5-21 carbon atoms, and n is an integer of 1 to
 6. 2. An inorganic filler-containing polyolefin composition of claim 1, which further comprises 0.01-1.0 part by weight of a sulfur antioxidant.
 3. An inorganic filler-containing polyolefin composition claim 1 or claim 2, which further comprises 0.01-2.0 parts by weight of a light stabilizer.
 4. An inorganic filler-containing polyolefin composition of claim 1, wherein an amount of the compounds represented by the general formulas (II) to (IV) is respectively 0.01-1.0 part by weight based on 100 parts by weight of polyolefin. 